From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A85EB1FC0E0 for ; Mon, 24 Feb 2025 22:21:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740435666; cv=none; b=YKqwEDE4etItsWlBPJAk4iJaThJGTJDULAC7qCe1buewEVvPBVqE4eIGWCWAs6/dCY06Yn4eTAug39Wh0sp9jZ5dYbDIUIJoBNeWMtEaOCDfd2O//fFYrGAIsCpdOn4HLQiPoI1a1WhYbSKTmeAWzB1nOXfkQrkC9vJc8jMSxQs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740435666; c=relaxed/simple; bh=vCBtutVOiqBw8zPVXIXZiaY8om9WDbsJ/tcVLA6Nx6g=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=ojn5cANIT+vLe2OJf8ZzMqDNJ6ALD8043IAEZ5xibuRaNc2pOJ+9vUujRyqQVXB4FUuy3oo3vevAyzztLFGRUPaLe2JHtmC1tKMMv3vAimCkdbqJs4uPFJcIjZB9H5J6sryMTjW8ixrbVFPlkr9v2vXmE5Tla+/WcDfCX57z1FQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sJN2lbHG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="sJN2lbHG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 138E0C4CED6; Mon, 24 Feb 2025 22:21:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1740435665; bh=vCBtutVOiqBw8zPVXIXZiaY8om9WDbsJ/tcVLA6Nx6g=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=sJN2lbHGx5xNFtmm2PNLy9iF+o/DBWaR5ZlXkgOMaGhU+i1j23ErY2B5hwtE0PHVp x/MQWRlShyJwPVHf5nQx6iHLzAEq5Hp+A4nOhJyU4UQKjG1V3TgjIiznzlCWqi1vl6 A6X6l9psarWMTWOqPS26szZgEl+I4TXITnQnAsc02wJBl/RKAYFR0/ct+dPVJMjMGt yhZZemiQxsV04roZb56FO7pcolnHQ9Z7V57sh5+xWUH1oDonQCeRMuB3C6l//IMXPn logbQMOfpUYdLIOKppBxyZn/ctp/WzHyFSHVJbvcqlnRAXSRda9aB8aM6QJFJwWye1 2f7HoiojvII1g== Date: Mon, 24 Feb 2025 14:21:04 -0800 From: Jakub Kicinski To: Willem de Bruijn Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, kerneljasonxing@gmail.com, pav@iki.fi, gerhard@engleder-embedded.com, vinicius.gomes@intel.com, anthony.l.nguyen@intel.com, Willem de Bruijn Subject: Re: [PATCH net-next] net: skb: free up one bit in tx_flags Message-ID: <20250224142104.14f44a27@kernel.org> In-Reply-To: <20250221035938.2891898-1-willemdebruijn.kernel@gmail.com> References: <20250221035938.2891898-1-willemdebruijn.kernel@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 20 Feb 2025 22:58:20 -0500 Willem de Bruijn wrote: > The linked series wants to add skb tx completion timestamps. > That needs a bit in skb_shared_info.tx_flags, but all are in use. > > A per-skb bit is only needed for features that are configured on a > per packet basis. Per socket features can be read from sk->sk_tsflags. > > Per packet tsflags can be set in sendmsg using cmsg, but only those in > SOF_TIMESTAMPING_TX_RECORD_MASK. > > Per packet tsflags can also be set without cmsg by sandwiching a > send inbetween two setsockopts: > > val |= SOF_TIMESTAMPING_$FEATURE; > setsockopt(fd, SOL_SOCKET, SO_TIMESTAMPING, &val, sizeof(val)); > write(fd, buf, sz); > val &= ~SOF_TIMESTAMPING_$FEATURE; > setsockopt(fd, SOL_SOCKET, SO_TIMESTAMPING, &val, sizeof(val)); > > Changing a datapath test from skb_shinfo(skb)->tx_flags to > skb->sk->sk_tsflags can change behavior in that case, as the tx_flags > is written before the second setsockopt updates sk_tsflags. > > Therefore, only bits can be reclaimed that cannot be set by cmsg and > are also highly unlikely to be used to target individual packets > otherwise. > > Free up the bit currently used for SKBTX_HW_TSTAMP_USE_CYCLES. This > selects between clock and free running counter source for HW TX > timestamps. It is probable that all packets of the same socket will > always use the same source. This needs a respin, presumably because Jason's series reached net-next already. -- pw-bot: cr